scholarly journals Intensification of tropical cyclones in the GFS model

2008 ◽  
Vol 8 (5) ◽  
pp. 17803-17839
Author(s):  
J. C. Marín ◽  
D. J. Raymond ◽  
G. B. Raga
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclones ◽  
Surface Friction ◽  
Sea Surface ◽  
Global Forecast System ◽  
Forecast System ◽  
Gfs Model ◽  
Environmental Air ◽  
The Relationship

Abstract. Special forecasts from the Global Forecast System (GFS) model were used in this study to evaluate how the intensification process in a tropical cyclone is represented in this model. Several tropical cyclones that developed in 2005 were analyzed in terms of the storm-scale circulation rather than more traditional measures such as maximum wind or minimum central pressure. The primary balance governing the circulation in the planetary boundary layer is between the convergence of environmental vorticity, which tends to spin up the storm, and surface friction, which tends to spin it down. In addition, we employ recently developed ideas about the relationship between precipitation and the saturation fraction of the environment to understand the factors controlling mass, and hence vorticity convergence. The budget of moist entropy is central to this analysis. Two well-known governing factors for cyclone intensification emerge from this study; surface moist entropy fluxes, dependent in the model on sea surface temperature and cyclone-generated surface winds, and ventilation of the system by dry environmental air. Quantitative expressions for the role of these factors in cyclone intensification are presented in this paper.

scholarly journals Intensification of tropical cyclones in the GFS model

2009 ◽  
Vol 9 (4) ◽  
pp. 1407-1417 ◽  
Author(s):  
J. C. Marín ◽  
D. J. Raymond ◽  
G. B. Raga
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclones ◽  
Surface Friction ◽  
Sea Surface ◽  
Global Forecast System ◽  
Forecast System ◽  
Gfs Model ◽  
Environmental Air ◽  
The Relationship

Abstract. Special forecasts from the Global Forecast System (GFS) model were used in this study to evaluate how the intensification process in a tropical cyclone is represented in this model. Several tropical cyclones that developed in 2005 were analyzed in terms of the storm-scale circulation rather than more traditional measures such as maximum wind or minimum central pressure. The primary balance governing the circulation in the planetary boundary layer is between the convergence of environmental vorticity, which tends to spin up the storm, and surface friction, which tends to spin it down. In addition, we employ recently developed ideas about the relationship between precipitation and the saturation fraction of the environment to understand the factors controlling mass, and hence vorticity convergence. The budget of moist entropy is central to this analysis. Two well-known governing factors for cyclone intensification emerge from this study; surface moist entropy fluxes, dependent in the model on sea surface temperature and cyclone-generated surface winds, and ventilation of the system by dry environmental air. Quantitative expressions for the role of these factors in cyclone intensification are presented in this paper.

scholarly journals Intensidade do vento de dois ciclones tropicais obtida por diferentes conjuntos de dados

2020 ◽  
Vol 13 (1) ◽  
pp. 067
Author(s):  
Christie Andre Souza ◽  
Michelle Simões Reboita
Keyword(s):  
Tropical Cyclones ◽  
The Other ◽  
Data Sets ◽  
Global Forecast System ◽  
Forecast System ◽  
Wind Intensity

Os ciclones tropicais quando atingem ventos com intensidade igual ou superior a 119 km/h desenvolvem uma estrutura conhecida como olho em seu centro. Já os ventos mais intensos do sistema são encontrados imediatamente após o olho. Num estudo recente para os ciclones Haiyan e Haima foi levantada a questão da qualidade dos dados do Global Forecast System (GFS) em representar os ventos uma vez que os ventos máximos apareceram no olho do sistema. Diante disso, esse estudo tem como objetivo avaliar como diferentes conjuntos de dados (GFS, ERA5, ERA-Interim e CCMP) representam os ventos nesses dois ciclones tropicais. A ERA5 e o GFS mostram ventos mais intensos nos ciclones do que os outros dois conjuntos de dados. Todos, exceto o GFS, mostram claramente ventos mais fracos no olho dos ciclones.  Wind intensity of two tropical cyclones obtained by different data sets A B S T R A C TWhen the tropical cyclones reach winds with intensity equal or higher than 119 km/h, they develop a structure known as the eye at its center. The strongest winds in the system are found immediately after the eye. In a recent study for Haiyan and Haima cyclones, the question of the quality of the Global Forecast System (GFS) data in representing the winds once the maximum winds appeared in the system eye was raised. Therefore, this study aims to evaluate how different data sets (GFS, ERA5, ERA-Interim and CCMP) represent the winds in these two tropical cyclones. ERA5 and GFS show cyclones with more intense winds than the other datasets. Except the GFS, the other data clearly show weaker winds in the cyclone eye.Keywords: analyzes; cyclones; meteorology; reanalysis

scholarly journals High-Resolution Ensemble HFV3 Forecasts of Hurricane Michael (2018): Rapid Intensification in Shear

2020 ◽  
Vol 148 (5) ◽  
pp. 2009-2032 ◽  
Author(s):  
Andrew T. Hazelton ◽  
Xuejin Zhang ◽  
Sundararaman Gopalakrishnan ◽  
William Ramstrom ◽  
Frank Marks ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Early Stage ◽  
Vertical Wind Shear ◽  
Vertical Shear ◽  
Rapid Intensification ◽  
Forecast System ◽  
The Mean ◽  
Cubed Sphere ◽  
Environmental Prediction ◽  
The Relationship

Abstract The FV3GFS is the current operational Global Forecast System (GFS) at the National Centers for Environmental Prediction (NCEP), which combines a finite-volume cubed sphere dynamical core (FV3) and GFS physics. In this study, FV3GFS is used to gain understanding of rapid intensification (RI) of tropical cyclones (TCs) in shear. The analysis demonstrates the importance of TC structure in a complex system like Hurricane Michael, which intensified to a category 5 hurricane over the Gulf of Mexico despite over 20 kt (10 m s−1) of vertical wind shear. Michael’s RI is examined using a global-nest FV3GFS ensemble with the nest at 3-km resolution. The ensemble shows a range of peak intensities from 77 to 159 kt (40–82 m s−1). Precipitation symmetry, vortex tilt, moisture, and other aspects of Michael’s evolution are compared through composites of stronger and weaker members. The 850–200-hPa vertical shear is 22 kt (11 m s−1) in the mean of both strong and weak members during the early stage. Tilt and moisture are two distinguishing factors between strong and weak members. The relationship between vortex tilt and humidification is complex, and other studies have shown both are important for sheared intensification. Here, it is shown that tilt reduction leads to upshear humidification and is thus a driving factor for intensification. A stronger initial vortex and early evolution of the vortex also appear to be the key to members that are able to resist the sheared environment.

scholarly journals Intense Precipitation Events Associated with Landfalling Tropical Cyclones in Response to a Warmer Climate and Increased CO2

2014 ◽  
Vol 27 (12) ◽  
pp. 4642-4654 ◽  
Author(s):  
Enrico Scoccimarro ◽  
Silvio Gualdi ◽  
Gabriele Villarini ◽  
Gabriel A. Vecchi ◽  
Ming Zhao ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Atmospheric Carbon Dioxide ◽  
Sea Surface ◽  
Special Focus ◽  
Relative Role ◽  
Rainfall Events ◽  
Landfalling Tropical Cyclones ◽  
Precipitation Changes ◽  
Precipitation Events

Abstract In this work the authors investigate possible changes in the intensity of rainfall events associated with tropical cyclones (TCs) under idealized forcing scenarios, including a uniformly warmer climate, with a special focus on landfalling storms. A new set of experiments designed within the U.S. Climate Variability and Predictability (CLIVAR) Hurricane Working Group allows disentangling the relative role of changes in atmospheric carbon dioxide from that played by sea surface temperature (SST) in changing the amount of precipitation associated with TCs in a warmer world. Compared to the present-day simulation, an increase in TC precipitation was found under the scenarios involving SST increases. On the other hand, in a CO2-doubling-only scenario, the changes in TC rainfall are small and it was found that, on average, TC rainfall tends to decrease compared to the present-day climate. The results of this study highlight the contribution of landfalling TCs to the projected increase in the precipitation changes affecting the tropical coastal regions.

scholarly journals Increasing vertical resolution in US models to improve track forecasts of Hurricane Joaquin with HWRF as an example

2016 ◽  
Vol 113 (42) ◽  
pp. 11765-11769 ◽  
Author(s):  
Banglin Zhang ◽  
Richard S. Lindzen ◽  
Vijay Tallapragada ◽  
Fuzhong Weng ◽  
Qingfu Liu ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Forecast Model ◽  
Vertical Resolution ◽  
Global Forecast System ◽  
Forecast System ◽  
Atlantic Basin ◽  
Hurricane Track ◽  
Environmental Prediction ◽  
The Impact ◽  
Positive Impacts

The atmosphere−ocean coupled Hurricane Weather Research and Forecast model (HWRF) developed at the National Centers for Environmental Prediction (NCEP) is used as an example to illustrate the impact of model vertical resolution on track forecasts of tropical cyclones. A number of HWRF forecasting experiments were carried out at different vertical resolutions for Hurricane Joaquin, which occurred from September 27 to October 8, 2015, in the Atlantic Basin. The results show that the track prediction for Hurricane Joaquin is much more accurate with higher vertical resolution. The positive impacts of higher vertical resolution on hurricane track forecasts suggest that National Oceanic and Atmospheric Administration/NCEP should upgrade both HWRF and the Global Forecast System to have more vertical levels.

scholarly journals Ekman Boundary Layers and Energy Dissipation in Rotating Drums During Spin-Down Process

1995 ◽  
Vol 2 (2) ◽  
pp. 113-121
Author(s):  
Hiroshi Ohue ◽  
Genshi Kawashima ◽  
Wen-Jei Yang
Keyword(s):  
Boundary Layer ◽  
Energy Dissipation ◽  
Fluid Motion ◽  
Light Sheet ◽  
Fluid Viscosity ◽  
Rotating Drum ◽  
Ekman Boundary Layer ◽  
Entire Flow ◽  
The Relationship

The Laser Doppler Velocimetry (LDV) is employed to investigate energy dissipation during a spin-down process inside a rotating drum. The tracer/light sheet method is applied to observe flow patterns in the entire flow field from which the instantaneous, two-dimensional velocity distribution and the formation and subsequent time wise variation of the Ekman boundary layer are determined. Results are synthesized to find the relationship between the Ekman boundary layer and the redistribution of secondary-flow induced angular momentum. The fluid viscosity, drum size and speed of rotation are varied to determine their effects on both the Ekman boundary layer and energy dissipation during spin-down process. The role of Ekman boundary layer in the reduction of rotating fluid motion is determined. Results from the study may be used to develop a method to achieve uniform mixing in an enclosed vessel.

scholarly journals Role of Planetary Boundary Layer Processes in the Simulation of Tropical Cyclones Over the Bay of Bengal

2018 ◽  
Vol 176 (2) ◽  
pp. 951-977 ◽  
Author(s):  
K. Vijaya Kumari ◽  
S. Karuna Sagar ◽  
Yesubabu Viswanadhapalli ◽  
Hari Prasad Dasari ◽  
S. Vijaya Bhaskara Rao
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclones ◽  
Planetary Boundary Layer ◽  
Bay Of Bengal ◽  
Boundary Layer Processes

scholarly journals The Role of Back Pressure in the Atmospheric Response to Surface Stress Induced by the Kuroshio

2017 ◽  
Vol 74 (2) ◽  
pp. 597-615 ◽  
Author(s):  
Kohei Takatama ◽  
Niklas Schneider
Keyword(s):  
Boundary Layer ◽  
Wind Stress ◽  
Back Pressure ◽  
Ocean Currents ◽  
Sea Surface ◽  
Ocean Current ◽  
Wind Stress Curl ◽  
General Response ◽  
The Kuroshio

Abstract The effect of ocean current drag on the atmosphere is of interest as a test case for the role of back pressure, because the response is independent of the thermally induced modulation of the boundary layer stability and hydrostatic pressure. The authors use a regional atmospheric model to investigate the impact of drag induced by the Kuroshio in the East China Sea on the overlying winter atmosphere. Ocean currents dominate the wind stress curl compared to the impacts of sea surface temperature (SST) fronts. Wind stress convergences and divergences are weakly enhanced even though the ocean current is almost geostrophic. These modifications change the linear relationships (coupling coefficients) between the wind stress curl/divergence and the SST Laplacian, crosswind, and downwind gradients. Clear signatures of the ocean current impacts are found beyond the sea surface: sea surface pressure (back pressure) decreases near the current axis, and precipitation increases over the downwind region. However, these responses are very small despite strong Ekman pumping due to the current. A linear reduced gravity model is used to explain the boundary layer dynamics. The linear vorticity equation shows that the oceanic influence on wind stress curl is balanced by horizontal advection decoupling the boundary layer from the interior atmosphere. Spectral transfer functions are used to explain the general response of back pressure to geostrophic ocean currents and sea surface height.

scholarly journals Deep Convective Organization, Moisture Vertical Structure, and Convective Transition Using Deep-Inflow Mixing

2019 ◽  
Vol 76 (4) ◽  
pp. 965-987 ◽  
Author(s):  
Kathleen A. Schiro ◽  
J. David Neelin
Keyword(s):  
Boundary Layer ◽  
Deep Convection ◽  
Convective Systems ◽  
Diurnal Cycles ◽  
Mesoscale Convective ◽  
Strong Relation ◽  
Environmental Air ◽  
Open Question ◽  
The Relationship ◽  
Convective Organization

Abstract It is an open question whether an integrated measure of buoyancy can yield a strong relation to precipitation across tropical land and ocean, across the seasonal and diurnal cycles, and for varying degrees of convective organization. Building on previous work, entraining plume buoyancy calculations reveal that differences in convective onset as a function of column water vapor (CWV) over land and ocean, as well as seasonally and diurnally over land, are largely due to variability in the contribution of lower-tropospheric humidity to the total column moisture. Over land, the relationship between deep convection and lower-free-tropospheric moisture is robust across all seasons and times of day, whereas the relation to boundary layer moisture is robust for the daytime only. Using S-band radar, these transition statistics are examined separately for mesoscale and smaller-scale convection. The probability of observing mesoscale convective systems sharply increases as a function of lower-free-tropospheric humidity. The consistency of this with buoyancy-based parameterization is examined for several mixing formulations. Mixing corresponding to deep inflow of environmental air into a plume that grows with height, which incorporates nearly equal weighting of boundary layer and free-tropospheric air, yields buoyancies consistent with the observed onset of deep convection across the seasonal and diurnal cycles in the Amazon. Furthermore, it provides relationships that are as strong or stronger for mesoscale-organized convection as for smaller-scale convection.

The Inland Maintenance and Reintensification of Tropical Storm Bill (2015) Part 1: Contributions of the Brown Ocean Effect

2021 ◽  
Author(s):  
Ryann A. Wakefield ◽  
Jeffrey B. Basara ◽  
J. Marshall Shepherd ◽  
Noah Brauer ◽  
Jason C. Furtado ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Land Surface ◽  
Heavy Rainfall ◽  
Tropical Storm ◽  
Sea Surface ◽  
Ocean Effect ◽  
Novel Approaches ◽  
Landfalling Tropical Cyclones ◽  
Water Vapor Budget

AbstractLandfalling tropical cyclones (TCs) often decay rapidly due to a decrease in moisture and energy fluxes over land when compared to the ocean surface. Occasionally, however, these cyclones maintain intensity or reintensify over land. Post-landfall maintenance and intensification of TCs over land may be a result of fluxes of moisture and energy derived from anomalously wet soils. These soils act similarly to a warm sea surface, in a phenomenon coined the “Brown Ocean Effect.” Tropical Storm (TS) Bill (2015) made landfall over a region previously moistened by anomalously heavy rainfall and displayed periods of reintensification and maintenance over land. This study evaluates the role of the Brown Ocean Effect on the observed maintenance and intensification of TS Bill using a combination of existing and novel approaches, including the evaluation of precursor conditions at varying temporal scales and making use of composite backward trajectories. Comparisons were made to landfalling TCs with similar paths that did not undergo TC maintenance and/or intensification (TCMI) as well as to TS Erin (2007), a known TCMI case. We show that the antecedent environment prior to TS Bill was similar to other known TCMI cases, but drastically different from the non-TCMI cases analyzed in this study. Furthermore, we show that contributions of evapotranspiration to the overall water vapor budget were non-negligible prior to TCMI cases and that evapotranspiration along storm inflow was significantly (p<0.05) greater for TCMI cases than non-TCMI cases suggesting a potential upstream contribution from the land surface.

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